1. Field of the Invention
The present invention relates to a communication control method for performing data communication between terminals in a complex switched network including a packet-switched network and a telephone network, and relates to a gateway using the control method. In this complex switched network, a communication system called Internet Telephony has become in practical use rapidly.
2. Description of the Prior Art
In recent years, high speed communication of voice data among personal computers on plural local area networks has been possible and practical as the development of network technology including wide band for the local area network (LAN), and the development of computer technology including multifunction of a personal computer (PC) and high speed of microprocessor. Application software and system for performing voice communication using conventional telephones among personal computers on the Internet including the LAN and a wide area network (WAN) are rapidly being available in the market. This kind of communication system is called the xe2x80x9cInternet Telephony.xe2x80x9d
In addition, an Internet telephony gateway (simply referred to as a gateway) has been developed, which has gateway function of protocol conversion between the telephone network and the Internet so as to realize communication therebetween. Furthermore, a communication system that uses the Internet telephony gateway for relaying the exchanges of the conventional telephone network by the Internet has been proposed and in practical use.
This communication system relaying the exchanges by the Internet is called bypass call between PBX (or route call between PBX) by the Internet Telephony. This telephone communication utilizing the bypass call between PBX by the Internet Telephony can be realized at lower cost than the telephone communication using the conventional telephone network, so this bypass call between PBX communication system is rapidly being used widely.
However, the above-mentioned bypass call between PBX communication system using the Internet telephony gateway has a disadvantage in communication quality such as sound quality compared with the conventional telephone network.
First, when sending and receiving data from and to the gateway on the Internet in the bypass call between PBX communication system, the communication data is compressed by a sound compression module (hereinafter, referred to as a CODEC), so that real-time communication can be performed. Therefore, the sound quality depends on the compression ratio of the CODEC. If the CODEC having large compression ratio is used, communication with low transmission speed can be possible though the sound quality is low. On the other hand, the CODEC having small compression ratio can realize good sound quality though high transmission speed is required. Thus, the sound quality and the transmission speed have relationship of tradeoff with each other.
Furthermore, there is a method in facsimile communication that does not need real-time communication, in which the calling side converts facsimile data into an e-mail format before sending it. Especially, when the quality of the Internet between the gateways is not high enough for the real-time processing, the method of converting facsimile data into an e-mail format before sending it is effective.
The above-mentioned method of transmission in real-time utilizing data compression by CODEC is called a xe2x80x9creal-time transmission,xe2x80x9d while the method of transmission after converting data into an e-mail format is called a xe2x80x9cstore-and-forward transmission.xe2x80x9d
The communication method between the gateways has many varieties of combination by selecting the circuit of gateway used for the bypass call between PBX, by selecting the real-time transmission or the store-and-forward transmission, and by selecting the CODEC (the compression ratio) used for the store-and-forward transmission.
Conventionally, the above-mentioned combination (i.e., the transmission method) is fixed for the bypass call between PBX communication system, and the user could not select the combination.
The object of the present invention is to provide the Internet telephony gateway that enables a user to select the transmission method for performing communication suitable for the situation unique to the user, and can select the efficient transmission method automatically if the user did not select the transmission method.
The communication control method in the complex switched network according to the present invention is applied to a complex switched network including a packet-switched network, a circuit switched network and a gateway that is connected to the packet-switched network and the circuit switched network via at least one circuit. The method includes the step in which the gateway selects one of plural data communication methods in accordance with a parameter input to the gateway or a circuit exchange. According to this communication control method, more effective communication method such as a communication path or a transmission format can be selected in the Internet telephony gateway system.
The selection of the data communication method includes selecting one of plural circuits to be used, selecting one of plural data compression means (CODEC) having different compression ratios, and selecting a data transmission format that is either the store-and-forward transmission or the real-time transmission.
Furthermore, the parameter used for selecting (switching) the communication method can be, for example, a dial number that is input to a telephone-equivalent terminal connected to the gateway or the circuit exchange, a user information of the calling side, a user information of the incoming side, a traffic of a packet-switched network that is measured in the gateway, or transmission contents that are sent for communication.
If the dial number that is input is used as the parameter, the user can select any communication path, transmission format or others by inputting a dial number for specifying the party to call. For example, the user can select the communication path or the transmission format having higher quality of service (QoS) if necessary.
The user information of the calling side, i.e., the user information of the caller can be input by an ISDN telephone or the equivalent as specifying the party to call. Using the user information of the calling side as the parameter, the communication path or the transmission format having higher QoS can be selected in accordance with the title of the caller, for example.
The user information of the incoming side, i.e., the user information of the receiver is transmitted from the incoming side to the calling side upon the incoming call. Using the user information of the incoming side as the parameter, the communication path or the transmission format having higher QoS can be selected in accordance with the title of the receiver, for example.
If the traffic of the packet-switched network measured in the gateway is used as the parameter, the gateway can select an efficient communication method automatically even in the case where the user did not select the communication method. Namely, the gateway can select the communication path, the transmission format or others having higher QoS in accordance with the traffic of the packet-switched network. For example, the circuit whose band used ratio as the traffic is low is selected, and the CODEC having higher compression ratio is selected if the band used ratio is not sufficiently low.
The transmission contents that are transmitted on communication has communication types, i.e., sound or facsimile, for example. If the transmission contents can be judged at an early stage of the communication, it can be used as the parameter for selecting (resetting) the transmission method, so that the communication method more suitable to the transmission contents can be selected automatically.
The gateway of the present invention that enables the above-mentioned communication control method includes a packet-switched network control portion connected to the packet-switched network, a circuit switched network control portion connected to the circuit switched network, and a call control portion for controlling a call of communication together with the packet-switched network control portion and the circuit switched network control portion, and for monitoring traffic of the packet-switched network, wherein the packet-switched network control portion includes a plurality of circuit connection portion that can be connected to plural circuits, and one of the plural circuits is selected as the circuit to be used in accordance with a parameter that is input to the gateway.
In a second configuration of the gateway of the present invention, the packet-switched network control portion includes plural data compression means having different compression ratios, and one of the plural data compression means is selected as the data compression means to be used in accordance with a parameter that is input to the gateway.
In a third configuration of the gateway of the present invention, the packet-switched network control portion includes a storage data processing portion for enabling store-and-forward type data transmission, and a data compression means for enabling real-time type data transmission, wherein either the store-and-forward type data transmission or the real-time type data transmission is selected in accordance with a parameter that is input to the gateway.